Stackers are commonly used in the newspaper and magazine industry wherein it is desired to handle the signatures comprised of magazines and folded newspapers and to form uniform bundles of a predetermined number of signatures. Signatures are typically delivered to the stacker in a continuous stream and are arranged in overlapping fashion. The delivery rate of signatures such as newspapers delivered from the press room can be at rates which produce a 12" bundle every second. Accordingly, it is necessary to provide a stacker which is capable of handling such a high speed continuous stream of signatures and forming accurate sized bundles at the rate of approximately one every second for extended periods of time and without failure. A breakdown of the stacker or jamming of the signatures in the stacker can result in shutdown of the entire printing system.
Conventional stackers are typically comprised of an infeed conveyor system which receives the continuous stream of signatures and which, in turn, is provided with means for counting the signatures as they pass through the infeed system. The signatures fall from the infeed system onto a stack support mechanism to thereby form bundles. When a suitable bundle is formed, the bundle is conveyed or dropped onto an outfeed conveyor. Means are further provided for periodically intercepting the stream of signatures at a location intermediate the infeed and the stack support mechanism while the bundles are conveyed from the stack support mechanism to the outfeed conveyor. The intercepting means forms a small bundle of signatures, and then deposits these signatures on the stack support mechanism once it has returned to an operable position.
Examples of prior art stackers are illustrated in the Sjogren et al. U.S. Pat. No. 4,037,525, issued July 26, 1977; the Wiseman U.S. Pat. No. 4,103,785, issued Aug. 1, 1978; the Wiseman U.S. Pat. No. 3,568,815, issud Mar. 9, 1971; and the Howdle et al. U.S. Pat. No. Re. 25,081, issued Aug. 8, 1961.
Attention is also directed the the Oderman U.S. Pat. No. 3,548,995, issued Dec. 22, 1970; the Loach et al. U.S. Pat. No. 3,379,320, issued Apr. 23, 1968; the Fujishiro U.S. Pat. No. 3,566,757, issued Mar. 2, 1971; and the Hedrick U.S. Pat. No. 3,599,807, issued Aug. 17, 1971.
Other prior art stacking devices are illustrated in the Anikanov et al. U.S. Pat. No. 3,831,781, Aug. 27, 1974; the Duchinsky et al. U.S. Pat. No. 3,861,537, issued Jan. 21, 1975; the Ohlsson U.S. Pat. No. 3,902,609, issued Sept. 2, 1975.
Attention is further directed to the Muller U.S. Pat. No. 4,139,191, issued Feb. 13, 1979; the Steinhart U.S. Pat. No. 4,183,704, issued Jan. 15, 1980; the Murchison et al. U.S. Pat. No. 3,429,239, issued Feb. 25, 1969; and the Lauren U.S. Pat. No. 3,362,707, issued Jan. 9, 1968.